Depolymerization using sonochemical reactors: A critical review

Ultrasonic irradiation has been proposed as a novel approach for degradation of polymer compounds, especially considering the fact that the reduction in the molecular weight (also the intrinsic viscosity) is simply by splitting the most susceptible chemical bond without causing any changes in the chemical nature. An overview of the application of ultrasound for the polymer degradation has been presented in this work, discussing the mechanism of degradation, kinetic modeling, effect of operating parameters and the type of reactors generally used for depolymerization. The effect of important operating parameters such as initial polymer concentration, presence of functional groups in the polymer chain, reaction volume, initial molecular weight, temperature, operating frequency, power dissipation and use of process intensifying additives have been discussed also giving guidelines about selection of the optimum parameters. It has been observed that the low concentrations and higher power dissipation (till an optimum) are favorable resulting in higher extents of degradation. Typically low frequency is recommended but for the case of water soluble polymers, higher frequencies would also give similar results due to the dominant action of chemical effects of cavitation. It has been demonstrated that the alkyl group substituent also affects the degradation rate of polymer. An overview of degradation using combined approach based on ultrasound and additives with comparison with individual approach has also been presented. It has been observed that the main contributing factor for the synergy of the combined approach is the selection of optimum loading of additives. Overall, it has been observed that efficient polymer degradation can be achieved using combined process based on the use of ultrasound.     

Two new ceramides from <Emphasis Type="Italic">Zephyranthes candida</Emphasis>

Two new ceramides were isolated from the bulbs of Zephyranthes candida. Their structures were established as (2S,3S,4R,13E)-1,3,4-trihydroxy-2-[(2′R)-2′-hydroxytetracosanoylamino]-13-octadecene, named zephyranamide A (1) and (2S,3S,4R)-1,3,4-trihydroxy-2-octacosanoylaminohexadecene, named zephyranamide B (2). The structures of the new compounds were elucidated by spectral techniques including ¹H NMR, ¹³C NMR, as well as HSQC, HMBC, DEPT, and COSY.     

Characterization of the core in full domain marriage problems

In this paper, we study the core of two-sided, one-to-one matching problems. First, in a model in which agents have strict preferences over their potential mates and are allowed to remain single, we characterize the core as the unique solution that satisfies individual rationality, Pareto optimality, gender fairness, consistency, and converse consistency. Next, in a model that relaxes the constraint that agents have strict preferences over their potential mates, we show that no solution exists that satisfies Pareto optimality, anonymity, and converse consistency. In this full domain, we characterize the core by individual rationality, weak Pareto optimality, monotonicity, gender fairness, consistency, and converse consistency.     

多孔纳米片状石墨相氮化碳的制备及其可见光催化

以三聚氰胺和硫脲为前驱体,通过简易的氧气刻蚀制备了多孔纳米片状氮化碳。相比于三聚氰胺制备的薄片状氮化碳（MCNS）,以硫脲制备的多孔纳米片状的g-C₃N₄（TCNS）片层更薄,其单片厚度约为30 nm,且TCNS的层状结构明显,能带隙约为3.03 eV,高于石墨相氮化碳（2.77 eV）,更宽的禁带赋予载流子更强的氧化还原能力。较大的比表面积（114 m²·g^-1）可以提供更多的活性位点,同时纳米片状结构可以促进电子与空穴的有效分离和转移,且能有效地降低光生载流子的复合率,因而TCNS具有更高的光催化活性。     

Green aspects during synthesis,application and chromatographic analysis of chiral pesticides

The agro-industry uses large quantities of chiral pesticides to mitigate the detrimental effects of pests on crops. Pesticides play a very important role of insuring food security in the world but this benefit may be eroded if principles of green chemistry are not embraced during their synthesis, application and analysis. Commercial chiral pesticide formulations are, usually, synthesised and sold as racemates. The enantiomers of the chiral pesticides in these racemic mixtures usually have enantioselective bioactivities on target organisms. One enantiomer, usually, will be active on the target organism while others are inactive and are discharged into the environment, posing serious pollution problems. This is a serious environmental problem and can be rectified through embracing general principles of green chemistry. This paper reviews the aspects that can enhance greenness during synthesis and the subsequent application of chiral pesticides during pest management in the agro-industry. Particular emphasis is placed on stereo-selective synthesis of chiral pesticides and the application of their enantiopure formulations. The green aspects during chromatographic separation of enantiomers of chiral pesticides are also discussed. These include the use of green mobile and chiral stationary phases during chromatographic analysis of chiral pesticides.     

Synthesis and bioactivity of novel strobilurin derivatives containing the pyrrolidine-2,4-dione moiety简

（E）-Methyl-2-（2-（bromomethyl）phenyl）-3-methoxyacrylate was reacted with substituted 1-acetylpyr-rolidine-2,4-diones and 3-（1-（hydroxylamino）ethylidene）pyrrolidine-2,4-diones respectively to synthesize two series of/%methoxyacrylate derivatives containing the pyrrolidine-2,4-dione moiety. The structures of the targeted compounds were confirmed by IR, 1H NMR, 13C NMR, MS and elemental analysis. The fungicidal activity against Rhizoctonia solani, Botrytis cinerea and Fusarium graminearum was evaluated. The bioassay results demonstrated that these compounds showed visible fungicidal activity.     

Extraordinary fast oxide ion conductivity in La1.61GeO5−δ thin film consisting of nano-size grain

Thin films of La_1.61GeO_5−δ, a new oxide ionic conductor, were fabricated on dense polycrystalline Al₂O₃ substrates by a pulsed laser deposition (PLD) method and the effect of the film thickness on the oxide ionic conductivity was investigated on the nanoscale. The deposition parameters were optimized to obtain La_1.61GeO_5−δ thin films with stoichiometric composition. Annealing was found necessary to get crystalline La_1.61GeO_5−δ thin films. It was also found that the annealed La_1.61GeO_5−δ film exhibited extraordinarily high oxide ionic conductivity. Due to the nano-size effects, the oxide ion conductivity of La_1.61GeO_5−δ thin films increased with the decreasing thickness as compared to that in bulk La_1.61GeO_5−δ. In particular, the improvement in conductivity of the film at low temperature was significant .The electrical conductivity of the La_1.61GeO_5−δ film with a thickness of 373 nm is as high as 0.05 S cm^− 1 (log(σ/S cm^− 1) = − 1.3) at 573 K.     

Unraveling the role of phase engineering in tuning photocatalytic hydrogen evolution activity and stability

In this work, taking NiSe₂ as a prototype to be used as cocatalyst in photocatalytic hydrogen evolution, we demonstrate that the crystal phase of NiSe₂ plays a vital role in determining the catalytic stability, rather than activity. Theoretical and experimental results indicate that the phase structure shows negligible influence to the charge transport and hydrogen adsorption capacity. When integrating with carbon nitride (CN) photocatalyst forming hybrids (m-NiSe₂/CN and p-NiSe₂/CN), the hybrids show comparable photocatalytic hydrogen evolution rates (3.26 μmol/h and 3.75 μmol/h). Unlike the comparable catalytic activity, we found that phase-engineered NiSe₂ exhibits distinct stability, i.e., m-NiSe₂ can evolve H₂ steadily, but p-NiSe₂ shows a significant decrease in catalytic process (∼57.1% decrease in 25 h). The factor leading to different catalytic stability can be ascribed to the different surface conversion behavior during photocatalytic process, i.e., chemical structure of m-NiSe₂ can be well preserved in catalytic process, but partial p-NiSe₂ tends to be converted to NiOOH.     

Determination of trace trichlorfon by high performance liquid chromatography with UV detection based on its catalytic effect on sodium perborate oxidizing benzidine

Trichlorfon has the capacity to catalyze the oxidation of benzidine (4,4′-diamino-biphenyl) to 4-amino-4′-nitro biphenyl in the presence of sodium perborate. The product of the catalyzed reaction was validated by LC-MS method. Reversed-phase high performance liquid chromatography with 365 nm UV detection was used for separation and quantification of 4-amino-4′-nitro biphenyl. It can be proven there is a linear relationship between the peak areas of 4-amino-4′-nitro biphenyl and trichlorfon in the concentration range of 0.02-0.5 mg L⁻¹ (r = 0.9988). Limit of detection was 2.0 μg L⁻¹. A method for the indirect determination of trichlorfon using HPLC was developed based on catalytic effect of trichlorfon. Method validation was performed on samples spiked at three levels (0.5, 1.0, 1.5 mg kg⁻¹), the recoveries ranged from 67.5 to 82.1%, with relative standard deviations between 4.5 and 7.3%.0.01 mol L⁻¹ sodium dodecyl sulphate (SDS) solution was used to extract trichlorfon from samples and solid-phase extraction was used to isolate and concentrate trichlorfon in SDS solution. The recoveries of trichlorfon obtained with percolating the extraction through a SPE system were essentially in agreement with those obtained by liquid-liquid extraction. This new isolation technique decreases the use of toxic solvents and satisfies the requirements of Green Analytical Chemistry.     

Novel Fluorinated 7-Hydroxycoumarin Derivatives Containing an Oxime Ether Moiety: Design,Synthesis, Crystal Structure and Biological Evaluation

A series of fluorinated 7-hydroxycoumarin derivatives containing an oxime ether moiety have been designed, synthesized and evaluated for their antifungal activity. All the target compounds were determined by ¹H-NMR, ¹³C-NMR, FTIR and HR-MS spectra. The single-crystal structures of compounds 4e, 4h, 5h and 6c were further confirmed using X-ray diffraction. The antifungal activities against Botrytis cinerea (B. cinerea), Alternaria solani (A. solani), Gibberella zeae (G. zeae), Rhizoctorzia solani (R. solani), Colletotrichum orbiculare (C. orbiculare) and Alternaria alternata (A. alternata) were evaluated in vitro. The preliminary bioassays showed that some of the designed compounds displayed the promising antifungal activities against the above tested fungi. Strikingly, the target compounds 5f and 6h exhibited outstanding antifungal activity against B. cinerea at 100 μg/mL, with the corresponding inhibition rates reached 90.1 and 85.0%, which were better than the positive control Osthole (83.6%) and Azoxystrobin (46.5%). The compound 5f was identified as the promising fungicide candidate against B. cinerea with the EC₅₀ values of 5.75 μg/mL, which was obviously better than Osthole (33.20 μg/mL) and Azoxystrobin (64.95 μg/mL). Meanwhile, the compound 5f showed remarkable antifungal activities against R. solani with the EC₅₀ values of 28.96 μg/mL, which was better than Osthole (67.18 μg/mL) and equivalent to Azoxystrobin (21.34 μg/mL). The results provide a significant foundation for the search of novel fluorinated 7-hydroxycoumarin derivatives with good antifungal activity.